It only loads one map segment for each map I select. I ask for a full install, it does the usual building of the index, takes a fraction of a second to build the map, and way too quick to download. I then re-run MapInstall, and it's only done a partial install (one map segment).

This is a known issue from an update to MapInstall/BaseCamp made last May. Garmin is aware of the issue and it has been a real pain in the arse for map developers like myself who create Windows installer packages to install maps into BaseCamp. Due to the lack of a fix from Garmin given how long this issue has been around, I wouldn’t expect a fix anytime soon. Map developers and consumers of Garmin and 3rd party maps should probably move in the direction of developing and consuming pre-compiles map images. There is a setting in GmapTools where you can make the .img file viewable in BaseCamp so there’s really no functionality lost other than not having them installed on your computer.

My feeling is that Garmin is trying to move away from PC installed maps and will only support map image files moving forward.

Strangely enough, just this week I sent two maps to my Garmin GPSMAP 66 using BaseCamp 4.7.0.0 and MAPInstall 4.2.0, and neither exhibited this commonly referenced failure. I was not expecting it to work, but it did. Both .img files are complete and fully functional on my GPSr.

Just sent a third map without issue. About 1.5GB - took about 15 minutes.

Are you running BaseCamp 4.7.0.0 and MAPInstall 4.2.0 on a PC (you did not specify)?

BaseCamp 4.7.0. I couldn't work-out what version of MapInstall I was running, so I downloaded and installed 4.2.0 and tried it again - same result (only loads 1 map segment). (I think I had 4.2.0 before anyway - the file dates appear to be the same)

Map developers and consumers of Garmin and 3rd party maps should probably move in the direction of developing and consuming pre-compiles map images. There is a setting in GmapTools where you can make the .img file viewable in BaseCamp so there’s really no functionality lost other than not having them installed on your computer.

So what do I need to do to get multiple maps into the GPS? Instead of downloading a Windows installer package for an OSM map, should I download an .img file, and give it a unique name and just whack it on the SD card? - and I can have multiple maps available for selection this way ?

Used a binary editor (UltraEdit) to change the map name inside the .img file to something more descriptive and unique other than "OSM generic routable" (the name is found at an offset of 49h into the .img file)

Copied the 2 .img files to the garmin directory on the SD card

Now I can select/de-select each map set in Map Setup > Configure maps

I would be better if MapInstall worked, but at least I have a work-around